The intensive care of a great many patients with respiratory difficulties, involves securing the air passage by means of a tube passing through the larynx into the windpipe. The prolonged use of such tubes is at present apt to cause ulceration of the larynx and trachea. Recent studies on laryngeal mechanisms indicate that the damage is caused by mismatch between the tube and the airway and trachea and suggest that new tubes designed on relevant biomechanical principles would correct these mismatches. This project proposes a quantitative determination of the extent of the present mismatch, using primate model and catheters equipped with pressure sensing devices. The data so obtained will guide the manufacture in the Bioengineering Workshop of the Universiy of Washington of biomechanically correct tubes. Inflation of the cuff required too seal the leak between tube and trachea is a frequent source of injury. The new tubes will dispense with cuff altogether. They will be tested in adult patients and the effects and aftereffects compared with those of conventional tubes, by means of fiberoptic photography. The results should provide a reliable estimate of the serviceability of the new tubes in critically ill infants, children and adults.